"Standard Operating Procedure" is an inquiry into the Abu Ghraib prison scandal that probes deeper than any other Iraq war documentary. It is not concerned with well-worn debates over whether the war should have been fought or is being successfully conducted. Oscar-winning documentary director Errol Morris scrutinizes the infamous torture snapshots showing American soldiers in grinning, thumbs-up poses beside naked and dead prisoners like a philosophical detective.

He raises fascinating questions about what happens to ordinary people in war zones, and whether a visual image of an event gives us a true picture. Often what occurs outside a picture's frame is crucial to understanding what it shows.

The foundation stones of Morris' film are the soldier's photographs, taken from three digital cameras. Time and again the film returns to the photos, powerful visual evidence of American misdeeds that prompted President Bush to issue an apology. Using data embedded in the photographs, Morris creates a timeline that connects the images, adding a greater sense of context to the events.

He also makes the crucial point that what those pictures omit is an important part of the story. We're told that private interrogations of prisoners involved greater tortures, with the approval of officers high up the chain of command.

Morris is a gifted interviewer and an imaginative storyteller. He brings together army investigators; a civilian interrogator; former Brigadier Gen. Janis Karpinski, who oversaw the Iraqi prison system; Pvt. First Class Lynndie England, and four more of the seven indicted MPs. Morris gets them to open up on camera, revealing human traits rarely glimpsed in media coverage of the affair. The servicemen and women rationalize their actions as the excesses of impressionable young recruits whose moral compasses failed in a place where harsh treatment of prisoners was taken for granted. Sgt. Jerval Davis describes the prison as a siege fortress under constant attack, staffed with unreliable Iraqi guards and holding angry, violent detainees. England says she posed for photos holding a prisoner on a dog leash because she was in love with the ringleader of the team, Specialist Charles Graner Jr.

Morris brings a filmmaker's sensibility to the process, reenacting key events, and using animation and special effects to highlight the action. Giving reality a helping hand galls documentary traditionalists, but Morris uses his cinematic techniques ethically and intelligently. Seeing a police dog, fangs bared, snapping at the camera in ultra-slow motion gives you a sense of how the interrogators used canines to intimidate the prisoners in a way no talking-heads interview could equal.

STANDARD OPERATING PROCEDURE

★★★ 1/2 out of 4 stars

Rating: R for disturbing images and content involving torture and graphic nudity, and for language.

Theater: Lagoon.

Yet Morris understands that images alone can't tell the story. The film insists that we consider what photographs can't show, the absence of leadership and accountability that enabled this military version of "Lord of the Flies" to exist.

Like a police procedural, the film shows how investigators sorted the 12 DVDs of photos into two groups. One showed evidence of criminal abuse; the other merely documented the stress and humiliation techniques considered standard operating procedure. Looking at one category and then the other, it's difficult to see exactly where the line was drawn, and easy to understand how in the stress of war the distinction between right and wrong could vanish altogether.